In a TFT-LCD (Thin Film Transistor-Liquid Crystal Display), each pixel unit has its corresponding thin-film transistor on the array substrate. The gate of the thin-film transistor is connected to the scan line (also called the row-scan line) in the horizontal direction, the drain is connected to the data line in the vertical direction, and the source is connected to the pixel electrode. When the display performs display, if a sufficient positive voltage is applied to a certain scan line in the horizontal direction, the control through the gate of the thin-film transistor will make all the thin-film transistors in the row turn on, and at this time the pixel electrodes corresponding to the thin-film transistors in the row will be connected to the data line in the vertical direction, thereby writing the display signal voltage transmitting on the data line into the pixel electrode, and further controlling the liquid crystals in the pixel unit area corresponding to the pixel electrode to reach different transparencies so as to achieve control of the grayscale and/or color displayed by the pixel unit.
Currently, the driving circuits of a TFT-LCD panel are mainly realized through bonding ICs (Integrated Circuit) to the outer edge of the panel, and the ICs are commonly manufactured by using silicon chips made of CMOS. Because the bonding ICs need to occupy a certain area and meanwhile the circuit design when the ICs are connected also occupies a certain area, the panel integration achieved by this way is not very high, also the occupied area thereof is large, both of which are disadvantageous to realize the high resolution and narrow frames of the display apparatus.
To solve this problem, there emerges the GOA (Gate Drive on Array) technique, in which the gate driver ICs of the TFT-LCD are directly and integratedly manufactured on the array substrate to substitute the driver chips made of silicon chips and bonded to the outer edge of the panel. Since the driver ICs can be directly manufactured on the array substrate by using this technique, and there is no need to bond ICs and wire around the panel. The production process of the panel is simplified, the product cost is reduced, and meanwhile the integration of the TFT-LCD panel is improved so as to realize the narrow border and the high resolution of the panel.
In the prior art, a conventional a-Si (amorphous Silicon) GOA circuit is usually implemented by using a pre-charge and boost circuit mechanism, and the shift register circuit thereof (Thomason circuit) is shown as in FIG. 1. When operating, the circuit makes use of STV signal (starting signal) phase to perform precharge (point P in the figure), thus achieving a shift output of a high-level square wave. This circuit includes four transistors T1-T4, two capacitors C1 and C2, an input signal for the previous stage Input(n−1), two clock signals CLK1 and CLK2, a reset signal for the next stage Reset(n+1), and the row output signal Row(n) formed under control of voltage Voff.
A latch is usually employed to compose an inverter in a conventional LTPS (Low Temperature Poly-silicon) GOA circuit, and at the same time transmission gates are used to perform control, a typical shift register circuit thereof is shown in FIG. 2. The circuit includes two latches (in the prior art, a latch is constituted of two inverters in series whose outputs are treated as the inputs of the registers, therefore four inverters included in the circuit), wherein one latch being used for programming and another latch being used for latching output signal. When operating, under control of two clock signals elk and clk_ as well as reset signal reset, the GOA circuit controls the programming of the latch and the output signal Q for the input signal D through the transmission gate.
It can be seen from the circuit structure shown in FIG. 1 and FIG. 2 that, GOA circuit of the prior art is relatively complex. Two capacitors are needed in the circuit shown in FIG. 1, which leads to the circuit occupying a relatively large space, and this is disadvantageous to narrow the border of a panel. At the same time, there is a floating status (a unconnected status in which the potential is uncertain) in the circuit, which leads to a lot of noise in the output level; 4 transmission gates and 2 latches are needed in the conventional shift register circuit as shown in FIG. 2, so the circuit is complex, and the complicated CMOS process, the cost of which is very high, must be used to implement it.